1. Field of the Invention
The present invention relates generally to measuring devices and, more particularly, to a method and apparatus for measuring the straightness of tubes.
2. Description of the Prior Art
Product specifications for precision tubing used in nuclear and aerospace applications, typically provide for straightness to be maintained along the tube length on the basis of a deviation per unit length of tubing. For example, a normal value for nuclear applications is 0.010 inch deviation per 12 inches of tube length.
In order to ensure proper quality control, it is required that manufacturers of aerospace and nuclear tubing certify that all tubing presented for customer acceptance has been tested for straightness and that all tubes meet the specified straightness criteria. Furthermore, the techniques and calibration methods employed by the manufacturers are subject to customer audit and approval. It is therefore, incumbent on the manufacturers to promote an accurate productive technique to check the straightness of precision aerospace and nuclear tubular product.
Presently, tubing is tested for straightness manually by rolling a tube across a reference surface plate and inserting a feeler gauge into the gaps occurring between the surface of the plate and the tube. Although all that is required with this method is a true flat surface and a set of feeler gauges, the method is time consuming and requires enough skill that a person carrying out the testing must have some training and experience to conduct the testing in a reasonable amount of time.